Method of treating soil for preemergent control of weeds



Patented Dec. 23, 1952 METHOD OF TREATING SOIL FOR PRE- EMERGENT CONTROL OF WEEDS Albert E. Hitchcock sand Percy W. Zimmerman, Yonkers, N. Y., assignors to Boyce Thompson Institute For Plant Research, Inc., Yonkers, N. Y., a corporation of New York No Drawing. Application June 30, 1950, Serial No. 171,573

1 Claim.

This invention relates to herbicides and has for its object the provision of an improved method of killing plants and especially the selective killing of certain plants. Our invention is based upon our discovery that chloroacetic acid has pronounced herbicidal properties and may be used in such concentrations as to kill many plants, or in certain critical concentrations to effect a selective killing of certain plants of a group of plants in the same area.

Chloroacetic acid is not only an efiective plant regulant but it has commercial and practical advantages because of its availability, low cost, and relatively high solubility in water. One of the unexpected and important characteristics of chloroacetic acid is that it can be readily taken up by one part of the plant and translocated to another part. If taken up by the roots, the

2 chemical goes into the plant and kills the top of the plant. If applied to the top of the plant, it will migrate to the roots where eventually the whole plant might be killed.

The chloroacetic acid has plant regulant properties when applied to various plants in concentrations from 0.10% to 10%. At concentrations of 3% to 1 0% the compound functions as a general herbicide, while at lower concentrations (0.3% to 3%) it functions as a selective herbicide whereby many common weeds may be killed entirely or partly without causing noticeable injury to certain crop plants such as corn, potatoes, grasses, gladioli, and. the like. The results of using aqueous spray solutions of chloroacetic acid are shown in the test of Table I. These tests show that sprays containing around 0.1% of the acid had no effect on either Weeds or crop plants.

TABLE I Minimum concentrations of chloroacetic acid (CHzClCOOI-I) sprays efiectioe for inducing the responses indicated. Entire plant sprayed unless otherwise noted Column N umber 1 2 3 4 5 Species Complete Complete Severe I Slight N plant top top top l kllllllg killing injury injury 1 111111137 Weeds:

1.0 1.0 0.32 0.1 0.1 1.0 1.0 0.32 0.1 0.1 1.0 1.0 0.32 0.1 0.1 1.0 1.0 0.32 0.1 0.1 3.2 3.2 1.0 0.32 0.1 1.0 1.0 0.32 0.1 0.1 1. 0 1. 0 0.32 0. 1 0. 1 1.0 1.0 0.32 0.1 0.1 1.0 1.0 0.32 0.1 0.1 1.0 1. 0 0.32 0.1 0.1 10.0 3. 2 1.0 0.32 0.1 Alligator weed. 10. 0 10. 0 3. 2 1. 0 1. 0 Algae l0. 0 10. 0 1. 0 1. 0 1. 0 Crop Plants:

Barley..- 1.0 1.0 1. 0 1.0 0.32

Buckwhea l. 0 1. 0 0. 32 0. 1 0. 1 4-6 00111- 10. 0 l0. 0 3. 2 1. 0 0. 32

18-24 Corn 10. 0 10. 0 10. 0 3. 2 1. 0

1 Considered tolerant. 9 Basal 4-6 sprayed.

3 Trace leaf spotting, no efiect on buds or stems. 4 Peach completely defoliated at 3.2 per cent with no injury to stem or buds. At 1.0 per cent partial defoliation (older leaves).

3 Some plants could be killed with 1% solutions, while others required up to 10%. For complete killing, solutions containing less than 1% were not effective. When applied at the rate of 20 to 40 pounds per acre as a pre-emergence spray 5 tubers.

TABLE II Results obtained by applying chloroacetic acid (CHzClCOOI-I) to the soil of tomato plants growing in four-inch pots. Three plants to each treatment 7 1.0% 0.32% 0.1% .No. cc. per 4 Pot Percent No. Percent No. Percent No.

Mgr/Pvt Km Days MEJPOt Kill Days M141? Kill Days 1 1 plant dead, 2 plants basal collapse in 6 days at 32 mg. per 4 pot rate of application.

to soil, chloroacetic acid kills young Weeds without causing injury to corn planted just before the spray is applied. Buds of potato tubers may be inhibited or killed without noticeable injury to the tuber. The effectiveness of soil applications of chloroacetic acid in killing young tomato plants (screening test) is illustrated in Table II.

Chloroacetic acid is selective in its action in the killing of many different kinds of plants. For example, crabgrass can be killed in late May or June without noticeable injury to Kentucky blue grass.

At the present time there is no satisfactory herbicide for applying to the weeds in rows of growing vegetables such as potatoes, carrots, cabbage, beans and the like where it is necessary to follow one crop with another. Chloroacetic acid exhibits no objectionable residual effect. In fact, seeds can be planted the day after spraying the soil.

Chloroacetic acid in suitable concentrations produces rapid killing and does not impart any objectionable taste to vegetables sprayed between the rows.

Chloroacetic acid may be applied in such concentrations as to effect a mere defoliation or to The following species Were not injured when CHzClCOOH was applied to the soil at the rate of 32 mg. per 4" pct:

Lawn grasses Barley Corn Sorghum We claim:

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Name Date Lean May 12, 1942 OTHER REFERENCES The Chemistry and Uses of Insecticides, by de Ong (1948), pages 1'73 and 174.

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